Reciprocating internal-combustion engine of the sleeve valve type



Oct. 19, 1954 A. T. EVANS 2,691,970

RECIPROCATING INTERNAL-COMBUSTION ENGINE OF THE SLEEVE VALVE TYPE Filed May 1, 1952 3 Sheets-Sheet l f A C r K 4\. b a C 65 QSYJ.

-V B B In uentor fir w. 1 y W Attorneys Oct. 19, 1954 EVANS 2,691,970

RECIPROCATING INTERNAL-COMBUSTION ENGINE OF THE SLEEVE VALVE TYPE Filed May 1, 1952 5 Sheets-Sheet 2 In ventpr Attorneys Oct. 19, 1954 A. T. EVANS 2,691,970

RECIPROCATING INTERNAL-COMBUSTION ENGINE OF THE SLEEVE VALVE TYPE Filed May 1, 1952 3 Sheets-Sheet 3 Invenior I Patented Oct. 19, 1954 N I-TIE "S TATES PATIEN T i 1 .O Ff-FIC E 'RECIPR'OCATING INTERNAL'JCOMBUSTION ENGINE OF THE SLEEVE VALVE TYPE Aubrey: Thomas Evans, west worthing, England,

assignor to-cRicardo & 00., Engineers (1927) 1 Limited, London, England, a: company of Great Britain Application-May l,:l952, Serial No. 285,390

Glaims-priority,: application Great Britain May 18, 1951 This invention relates to reciprocating internal combustion engines of the sleeve va'lve'type and of the kind in which the ports in each cylinder are controlled by a single sleevevalve having imparted to it a combined oscillating and reciproeating movement such that each point on the sleeve follows a path relatively to the cylinder surface which in development is approximately circular or oval.

Hitherto in order to provide an appropriate time-area diagram for each port opening during each cycle, when employing sleeve valves of the kind in question, that is to say a time-area diagram representing a suitably rapid increase in open port area during the-initial opening period and a similarly suitably rapid reduction in open port area during the final closing period to ensure adequate breathing capacity,'each of the ports respectively in the cylinder and in the sleeve valve have been made of approximately triangular form With the apices of the triangle rounded.

Various methods have been used for making such ports in the sleeve valves, for example profile milling, filing, either free-hand or to a-flling guide, and, in the case-of sleeve valves formed method cannot be used on sleeve valves of certain materials, including cast iron.

In many cases, particularly where very small engines to be produced inlarge-quantities are concerned, savin of time in manufacture is of great importance, and whereas the cylinders of such engines, particularly when made of light alloy, can be made by die-casting methods with the ports formed in the die-casting operation so that. no further port cutting is necessary, a similarly rapid method of production has not been available for the sleeve valves, when made in materials unsuitable for punching, for example in thin cast iron which from many aspects it may be desirable or necessary to use withsuch die-cast cylinders.

An object of the present invention is to reduce or overcome this difference by enabling. sleeve valves for engines of the kind in question, and more especially comparatively small engines, to

be produced more rapidly and cheaply than Moreover although the invention is ports cannot be formed by punching, it is to be understood that it may also be applied to engines having sleeve valves of a material. such that the ports could be formed by punching.

In a reciprocating internal combustionengine of the kind referred to according .to the present invention, each port in the sleeve valve or in each sleeve valve is of circular contour and the 00- operating port in the cylinder wall has a contour including convex portions projecting into the p'ortarea and each having a radius of curvature approximately equal to that of the sleeve port, these convex portions being disposed respectively in the side of the cylinder port across which an edge of the sleeve port passes as the sleeve port comes into communication with the cylinder port and in the side of the cylinder port across which an edge'portion of the sleeve'port passes as the sleeveport moves out of communication with the cylinder 'p-ort. Thus it. will be seen that a substantial arc of the. sleeve .port contour. passes across a corresponding arc of the'cylinder' port contour represented by oneof the convex portions at the moment when the ports. come into communication While similarly a substantial arc of the sleeve port contour passes across a corresponding arc of the cylinder port contour represented by the other convex projection, at the moment that the ports move out ofcommunication.

In this way a satisfactory time-area diagram for the port opening can be provided withcircular ports in the sleeve. I

It will also be apparent that such'circularports can be formed in the sleeve by simple drilling operations and/or by other simple and-rapid machining operations such as are impossible" where a contour other than circular" is required.

One particularly convenient application of the invention is to small engines of the kind in question in which the cylinder or each cylinder is formed by die-casting with the ports therein formed in the die-casting process, for example an engine of the kind forming the subject of United States Patent Application Serial No. 172,805, filed July 10, 1950, and now abandoned. It will beseen that the sleeve valve or valves may. then be made of cast iron or other selected materialandhave the ports formed in them by simple drilling operations, for example in a jig which. determines the positions of the ports in the sleevein relation to the pin, socket or other part on the "sleeve throughswhich its combined oscillating and reciprocating movement is imparted to it, whereby thesleeves can be produced with a rapidity'bear ing a reasonable relationship'.to:that withwhich the die-cast cylinders can be produced and the mass production of the engines as a whole is therefore facilitated.

One form of the invention as applied to such an engine is therefore illustrated by way of example in the accompanying drawings, in which Figure l is a sectional elevation of the complete engine taken in a plane containing the axis of the cylinder and the axis of the crankshaft,

Figure 2 is a cross-section through the cylinder in a plane normal to its axis and at the position at which the inlet and exhaust ports are formed therein,

Figure 3 is an enlarged diagrammatic view of one form which the cylinder inlet port and sleeve inlet port may take to illustrate this form of these ports and the manner in which they cooperate.

Figure 4 is a similar view to Figure 3 showing one form which the cylinder exhaust port and the sleeve exhaust port may take showing how they cooperate, and

Figures 5 and 6 are similar views to Figures 3 and 4 showing respectively alternative forms which the inlet and exhaust ports in the cylinder may take.

The engine shown in Figures 1 and 2 comprises a crank case A in which the usual crankshaft B is supported in bearings B this crankshaft carrying a combined flywheel and driving pulley B at one end and the rotary part C of a magneto at its other end for supplying the usual ignition impulses to the sparking plug C Mounted upon the crank case A is an air-cooled cylinder D having an inlet port D and an exhaust port D these two ports lying diametrically opposite to one another, as shown in Figure 2, and. being of such conformation, as described in the specification of United States Patent Application No. 172,805 that the cylinder with the ports therein can be formed by die-casting. The outer end of the cylinder B is closed by the usual cylinder head E and the cylinder contains a sleeve valve F having inlet and exhaust ports F F therein which cooperate with the ports D and D in the manner hereinafter more fully described.

Mounted upon the crankshaft B is a gear wheel G which meshes with a gear wheel G on a layshaft G so as to drive the layshaft at half crankshaft speed. The layshaft G which is supported in bearings G carries a crank pin G at one end arranged to impart a combined oscillating and reciprocating movement to the sleeve F in known manner through the medium of a ball joint G located within a socket F formed on the sleeve F.

A starting handle H can be caused to rotate the layshaft G through a dog clutch H for starting purposes in a well-known manner.

The ports D D which communicate respectively with inlet and outlet passages D D formed in the cylinder in one example have respectively the contours shown on an enlarged scale in Figures 3 and 4, while the ports F F are of circular form, as also shown in Figures 3 and 4, having been formed by drilling the sleeve F at the required points, the port F being shown in Figure 3 in two positions indicated respectively by the lines I. O. and I. C., while the port F is shown in Figure 4 in two positions indicated respectively by the lines E. O. and E. C.

It will be appreciated that the chain dotted lines K and K in Figures 3 and 4 represent in the normal manner the locus of the centre point of the ports F and F respectively, while the arrows indicate the direction of movement of this point during operation.

As will be seen, the cylinder inlet port D in Figure 3 may be regarded as being of approximately rectangular form except for two convex portions J and J extending into it at the points from which respectively the port F approaches it immediately prior to the opening of the inlet ports and at the point where the port F recedes from it immediately after the closing of the inlet ports. These projections J, J have a radius of curvature approximately equal to that of the port F and are arranged as shown so that a substantial length of the circumference of the port F passes simultaneously over the edge of the projection J at the moment of opening of the ports, while similarly a, substantial length of the circumference of the port F passes simultaneously over the edge of the projection J at the moment of closing of the ports.

The exhaust port D is similarly provided with projections J 3 and J of the same radius of curvature as the port F and disposed so that a substantial length of the circumference of the port F passes over the edge of the projection J at the moment of opening of the exhaust ports and passes over the edge of the projection J at the moment of closing of the exhaust ports.

In the modified form which the ports D and D may take as shown in Figures 5 and 6 in which the ports are shown in the same relative positions as in Figures 3 and i, it will be seen that the port D is provided with projections J and J 6 corresponding to the projections J and J but considerably deeper than them so that the configuration of the port D is much further removed from a rectangle than in Figures 3 and 4 while moreover a more rapid rate of opening and closing of the inlet ports is provided. Similarly the port D has projections J J corresponding to the projections J J in Figures 3 and 4 but considerably deeper than them so that the port D has a form which is considerably removed from that of a rectangle and a more rapid opening and closing of the exhaust ports takes place.

In the arrangement shown in Figures 5 and 6 the ports D and D are shown as extending in directions away from the loci K and K further than is actually required to provide maximum port opening at the appropriate times. While such an arrangement may be convenient in some cases for ease of construction, therefore, the form of these ports may be modified so that the sides thereof remote from the loci K and K follow the contour indicated by the chain lines L and L that is to say a contour such that for a substantial part of the opening period of each of the ports the edge of the port F or F will coincide with the edge L or L of the port D or D In the example described the swept volume of the engine would normally be less than 100. cubic centimetres while the bore of the sleeve might be, for example, 3.18 centimetres, the stroke of the piston approximately 3.8 centimetres, and the stroke of the sleeve about 1.5 centimetres, that is to say about 40% of the piston stroke, the arrangement being such that the piston speed at which maximum power is obtained is between 1000 and 1590 feet per minute.

It is to be understood, however, that, although the invention has been described with particular reference to a small sleeve valve engine of the kind referred to and of the general character described in the specification of United States Pat-- ent application Serial No. 172,805 the invention is applicable to sleeve valve engines of the kind referred to having one or more inlet ports and one or more exhaust ports in the cylinder and sleeve valve or each cylinder and sleeve valve and irrespective of the dimensions, swept volume and other dimensional characteristics of the engine.

What I claim as my invention and desire to secure by Letters Patent is:

1. A reciprocating internal combustion engine including at least one cylinder having at least one port in its wall for the passage of gaseous matter, a sleeve valve within the cylinder and means for imparting to the sleeve a combined oscillating and reciprocating movement, wherein the port in the sleeve is of substantially circular contour and the port in the cylinder Wall has a contour including convex portions projecting into the port area and each having a radius oi curvature approximately equal to that of the contour of the port in the sleeve, these convex portions being disposed respectively in the side of the cylinder port across which the edge portion of the sleeve port passes as the sleeve port comes into communication with the cylinder port and the part of the edge of the cylinder port across which an edge of the sleeve port passes as the sleeve port moves out of communication with the cylinder port.

2. A reciprocatin internal combustion engine including at least one cylinder having inlet and exhaust ports in its walls, a sleeve valve within the cylinder having inlet and exhaust ports formed therein to cooperate with the inlet and ex haust ports in the cylinder Wall for the admission of a gaseous charge and the exhaust of prod nets of combustion, and means for imparting to the sleeve valve a combined oscillating and reciprocating movement, wherein each port in the sleeve is of substantially circular contour and each port in the cylinder has a contour includin convex portions projecting into the port area and each having a radius of curvature approximately equal to that of the contour of the cooperating port in the sleeve, these convex portions being disposed respectively in the side of the cylinder port across which an edge or the sleeve port passes as the sleeve port comes into communication with the cylinder port and in the side of the cylinder port across which an edge portion of the sleeve port passes as the sleeve port moves out of communication with the cylinder port.

3. A reciprocating internal combustion engine as claimed in claim 2 in which one of the convex portions of each cylinder port contour extends alon the greater part of the edge of the cylinder port adjacent to the cylinder head while the other extends along the greater part of the appropriate side of the cylinder port with a tongue-like portion of, the cylinder port extending between the two convex ports from the wider part of the port.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,131,266 Phillips Mar. 9, 1915 1,237,054 Keister Aug. 14, 1917 2,911,820 Meyer Aug. 20, 1935 2,2e2,8'71 Raab et a1 May 20, 1941 2,444,103 Kuhn June 29, 1948 

